The NICHD Collaborative Pediatric Critical Care Research Network (CPCCRN, UG1) was established in 2004 to address the following: (1) increased utilization of costly and complex pediatric critical care services and (2) lack of prospective clinical trials in pediatric critical care compared with adult and neonatal populations The primary Aim of this application is to join the CPCCRN as a clinical site, in order to expand our single center prospective observational cohort of pediatric patients with Acute Respiratory Distress Syndrome (ARDS) through enrollment at multiple CPCCRN Sites. ARDS is a common cause of pediatric critical illness (30% of PICU mortalities). We propose to enroll 800 pediatric patients with ARDS and collect clinical data with plasma and genetic biomarkers of coagulation and inflammation. The data obtained will be essential for stratifying prospective clinical research trials and will provide insight into basic molecular and cellular disease mechanisms necessary for designing new treatments. UCSF Medical Center and Benioff Children's Hospital, the Department of Pediatrics and Division of Pediatric Critical Care Medicine have a long history of participation in ground breaking multicenter clinical research, as well as cutting edge individual investigator driven basic, translational and clinical research. This tradition, coupled with deep institutional resources for biomedical research, makes our center ideally positioned to contribute novel proposals to the consortium and participate fully in network-sponsored studies